udp的广播和组播（udp 广播）

以下是Windows平台下基于Winsock的

接收的示例代码：

 #include <stdio.h> #include <stdlib.h> #include <winsock2.h>  #define MULTICAST_IP "224.0.0.1" // 组播 IP地址 #define LOCAL_IP "192.168.1.100" // 本地IP地址 #define PORT 8888 // 端 口号 #define MAX_BUF_LEN 1024 // 缓冲区大小  int main() { // 初始化Winsock WSADATA wsaData; if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) { printf("WSAStartup failed with error code %d ", WSAGetLastError()); return 1; }  // 创建套接字  SOCKET sock = socket (AF_INET, SOCK_DGRAM, IPPROTO_ UDP ); if (sock == INVALID_ SOCKET ) { printf(" socket failed with error code %d ", WSAGetLastError()); WSACleanup(); return 1; }  // 绑定本地IP地址和 端 口号 struct sockaddr_in localAddr; localAddr.sin_family = AF_INET; localAddr.sin_addr.s_addr = inet_addr(LOCAL_IP); localAddr.sin_port = htons(PORT); if (bind(sock, (struct sockaddr*)&localAddr, sizeof(localAddr)) == SOCKET _ERROR) { printf("bind failed with error code %d ", WSAGetLastError()); close socket (sock); WSACleanup(); return 1; }  // 加入 组播 组 struct ip_mreq mreq; mreq.imr_multiaddr.s_addr = inet_addr(MULTICAST_IP); mreq.imr_interface.s_addr = inet_addr(LOCAL_IP); if (setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char*)&mreq, sizeof(mreq)) == SOCKET _ERROR) { printf("setsockopt failed with error code %d ", WSAGetLastError()); close socket (sock); WSACleanup(); return 1; }  // 接收数据 char buf[MAX_BUF_LEN]; struct sockaddr_in fromAddr; int fromLen = sizeof(fromAddr); int recvLen; while (1) { recvLen = recvfrom(sock, buf, MAX_BUF_LEN, 0, (struct sockaddr*)&fromAddr, &fromLen); if (recvLen > 0) { buf[recvLen] = '0'; printf("Received message from %s: %s ", inet_ntoa(fromAddr.sin_addr), buf); } }  // 退出 组播 组 if (setsockopt(sock, IPPROTO_IP, IP_DROP_MEMBERSHIP, (char*)&mreq, sizeof(mreq)) == SOCKET _ERROR) { printf("setsockopt failed with error code %d ", WSAGetLastError()); close socket (sock); WSACleanup(); return 1; }  // 关闭套接字 close socket (sock);  // 清理Winsock WSACleanup();  return 0; } 

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